The present invention relates to handling and robotics systems, in general, and to such in semiconductor processing control systems, in particular.
Reference is made to FIG. 1, which illustrates a prior art process environment 10 in a semiconductor fabrication plant. In general, process environment 10 comprises a process unit 2, such as a chemical mechanical polisher, at least one load/unload cassette station 4 (two are shown), an integrated metrology tool 6 and a robot 8.
The robot 8 transfers wafers to and from both the processing unit 2 and the cassette stations 4. However, the integrated metrology tool 6 requires its own handling system in order to transfer the wafer to be measured from the robot 8 to a measuring location on tool 6 and vice versa.
FIGS. 2A, 2B, 2C, 2D, 2E and 2F illustrate the operation of tool 6 and robot 8 using a handling system 16 to work with an integrated metrology tool having a measuring unit 15. One exemplary process environment uses the NOVASCAN 210 integrated metrology tool, commercially available from Nova Measuring Instruments Ltd. of Rehovot, Israel, and its handling system. The handling system 16 is composed of a bent arm 17 connected to a gripper 18. The latter can be any gripper that can hold a wafer, such as a vacuum gripper.
The arm 17 slides vertically on a vertical rail 14 and reaches above the measuring unit 15 in order to place a new wafer in a measuring position and/or to return a measured wafer to the robot 8. Between the uppermost position of gripper 18 and measuring unit 15 there is a supporting station 19 comprised of two supporting beams 24 and 25, each of which has a supporting base 26. Supporting beams 24 and 25 are connected to a rail 30 by a relative motion unit 32. Unit 32 is designed to provide relative motion to supporting beams 24 and 25 such that they move toward and away from each other, as indicated by arrows 34 and 36. A coupling member 54 connects supporting station 19 to the measuring unit 15.
As shown in FIG. 2B, with supporting beams 24 and 25 in their most separated positions, gripper 18 can freely pass through the buffer station 22, even when loaded with a wafer. As shown in FIG. 2C, with supporting beams 24 and 25 in their closest positions, a wafer can be held on each of supporting base 26 and gripper 18 cannot pass through.
In operation, and as shown in FIG. 2D, the robot 8 arrives at integrated tool 6 loaded with a new wafer W on an arm 9. At this point, handling system 16 is waiting in its uppermost position. Robot 8 places the wafer W on supporting bases 26, after which, as shown in FIG. 2E, handling system 16 moves down and picks up the wafer W. Robot 8 then leaves integrated tool 6 to conduct other missions while handling system 16, loaded with the wafer W, continues down, until, as shown in FIG. 2E, it places the wafer, working surface down, in a measuring position on the measuring unit 15. Typically, the measuring position includes supports that support the wafer on its edges (not shown). Since supporting beams 24 and 25 have moved towards and away from the plane of the paper, the supporting station 19 is shown in FIG. 2F with dashed lines.
It is noted that robot 8 leaves tool 6 empty and must arrive at tool 6 unloaded in order to take back a measured wafer. Thus, robot 8 is not optimally exploited, i.e., a disadvantage considering that the robot 8 is the xe2x80x9cbottle neckxe2x80x9d in process environment 10 (FIG. 1).
Prior art systems solve this problem in multiple ways. One exemplary robot is the DBM 2400 series of Equipe Technologies, Mountain-View, Calif., USA. This robot has two separate arms. A second exemplary robot is the PerMer 6100 robot of Cybeq Systems, Sunnyvale, Calif., USA. The robot can hold two wafers, one on each side of its arm, and rotates the arm 180 degrees in order to switch wafers. For both prior art systems, the robot arrives at the supporting station loaded with a new wafer, and the free arm or side faces the supporting station. The free arm (side) loads a processed wafer from the supporting station, after which, the arm (side) with the new wafer is loaded onto the supporting station. The robot then returns loaded with the processed wafer.
It will be appreciated that these solutions require additional footprint since, during their operation, the two arms (sides) are loaded with both new and processed wafers. This may be a drawback in crowded processing environments.
It is therefore an object of the present invention to overcome the aforementioned limitations of the prior art.
There is thus provided in accordance with a preferred embodiment of the present invention a buffer station for an article handling system, the handling system having a general path along which it moves when handling the article, the buffer station comprising at least two supporting assemblies comprising supporting elements forming a supporting plane each capable of supporting an article within said supporting plane and located so as to support said article within said general path, at least two receptacles for liquid in which said at least two supporting assemblies are disposed and at least two drivers associated with said at least two supporting assemblies and said receptacles for shifting them in and out of said general path.
In accordance with a preferred embodiment of the present invention the supporting elements include at least two supporting bases each capable of holding a wafer thereon when the supporting elements are in the first mode.
There is also in accordance with a preferred embodiment of the present invention a buffer station for a wafer handling system, the handling system having a general path along which it moves when handling the wafer, the buffer station including at least two pairs of supporting elements each capable of supporting at least one wafer therebetween and located so as to support the wafer within the general path, a receptacle in which at least one of the pairs of supporting elements are disposed, the receptacle being at least partially filled with a liquid and adapted to hold at least one wafer at least partially submerged in the liquid, and one motion unit per pair of supporting elements for shifting its associated pair of supporting elements in and out of the general path and when the supporting elements are in the general path, for providing relative motion to its associated pair of supporting elements such that, in a first mode, the supporting elements support the wafer within the general path and, in a second mode, the supporting elements are sufficiently separated so as not to disturb the motion of the handling system when the handling system holds a wafer.
In accordance with a preferred embodiment of the present invention each of the supporting elements includes at least one supporting base each capable of holding a wafer thereon when the supporting elements are in the first mode.
Further in accordance with a preferred embodiment of the present invention the at least one supporting base includes two supporting bases.
Still further in accordance with a preferred embodiment of the present invention the at least two pairs of supporting elements include at least three pairs of supporting elements.
Additionally in accordance with a preferred embodiment of the present invention a liquid reservoir is in fluid communication with the receptacle.
In accordance with a preferred embodiment of the present invention a recirculation conduit is in fluid communication with the receptacle and the liquid reservoir, adapted to recirculate a liquid between the receptacle and the liquid reservoir. The liquid reservoir may be a source of purified, e.g. distilled water.
Further in accordance with a preferred embodiment of the present invention the receptacle includes a flexible, foldable gate, which when closed substantially seals flow of liquid from the receptacle.
There is also provided in accordance with a preferred embodiment of the present invention a processing unit for processing at least one semiconductor wafer, the unit including a processing station for processing the at least one wafer, a measuring station for measuring the at least one wafer, a robot for moving the at least one wafer between the processing and measuring stations, a wafer handling system operating in conjunction with the measuring station for moving the at least one wafer to and from a measuring location on the measuring unit, a buffer station associated with the wafer handling system for receiving measured and unmeasured wafers thereby to enable the robot to arrive at and leave the measuring station with at least one wafer thereon, and a receptacle in which the buffer station is disposed, the receptacle being at least partially filled with a liquid and adapted to hold the at least one wafer at least partially submerged in the liquid.
In accordance with a preferred embodiment of the present invention at least one of the supporting elements is movable along and connected to a centering driver.
Further in accordance with a preferred embodiment of the present invention there is also provided a foldable gate, which when closed substantially seals flow of liquid from said receptacle.
Still further in accordance with a preferred embodiment of the present invention the gate is flexible.
In accordance with a preferred embodiment of the present invention each of the supporting assemblies comprise at least two supporting elements forming the supporting plane.
Further in accordance with a preferred embodiment of the present invention the supporting assemblies comprise at least three supporting elements forming the supporting plane.
The buffer station may be provided with receptacles having one or more conduits in fluid communication with a liquid source, along with one or more drain conduits that are preferably provided with one or more drain valves operable by a control unit.
Preferably the liquid used in the buffer station is purified or distilled water.
Additionally in accordance with a preferred embodiment of the present invention the buffer station may include a pre-alignment unit located within a general path of said handling system.
Still further in accordance with a preferred embodiment of the present invention the pre-alignment unit is movable in and out said general path or is tilted with respect to a general path of said handling system.